Preheat oven to 325°F for 10 minutes. Grease the inside of a loaf pan with butter or nonstick spray, then dust with flour and tap out excess. (Alternatively, line with parchment paper for easier removal.) This prevents sticking and creates an even crust.

In a small mixing bowl, combine 2 cups all-purpose flour, 1/2 teaspoon baking powder, and 1/2 teaspoon salt. Whisk together for 30 seconds until combined. Set aside on the counter.

In a large mixing bowl, place 1 cup softened unsalted butter (it should be soft enough to dent with your finger but not greasy). Add 1 1/2 cups granulated sugar. Using an electric mixer on medium speed, beat for 3–4 minutes, scraping the bowl halfway through. The mixture should look pale, fluffy, and light—like thick frosting. Checkpoint: You should see ribbons of mixture fall from the beaters when you lift them.

Crack the first egg into a small cup, then add it to the butter mixture. Beat on medium for 30 seconds until fully combined. Repeat with the remaining 3 eggs, one at a time, beating 30 seconds after each addition. If the mixture looks curdled (lumpy), it's okay—it will smooth out.

Add 1 teaspoon vanilla extract and 2 tablespoons lemon zest to the bowl. Beat on medium for 30 seconds until the zest is evenly distributed and the mixture is light yellow.

Turn the mixer to low speed. Add 1/3 of the flour mixture and mix for 20 seconds until just barely combined. Scrape down the bowl.

Add 1/2 of the 1/2 cup sour cream (about 1/4 cup) and mix on low for 15 seconds. Scrape down the bowl again.

Add another 1/3 of the flour mixture and mix on low for 20 seconds. Scrape the bowl.

Add the remaining 1/4 cup sour cream and mix on low for 15 seconds.

Add the final 1/3 of the flour mixture and mix on low for 20 seconds until just combined. Do not overmix. Checkpoint: The batter should be thick, creamy, and no streaks of flour should be visible.

Turn the mixer off. Pour in 1/4 cup fresh lemon juice slowly while stirring by hand with a spatula for 10 seconds until just combined. The batter may look slightly curdled, but this is normal.

In a separate small bowl, place 1 1/2 cups fresh raspberries and sprinkle with 2 tablespoons all-purpose flour. Gently toss with a fork for 15 seconds, coating each berry lightly. This prevents them from sinking to the bottom of the cake.

Using a spatula, gently fold the floured raspberries into the batter with 5–8 slow, careful folding motions. Mix just until the berries are evenly distributed. A few streaks are fine—do not overmix, or the berries will break down and turn the batter purple.

Pour the batter into the prepared loaf pan, filling it about 3/4 full. Gently tap the pan on the counter 2–3 times to release air bubbles. Using a spatula or the back of a spoon, smooth the top into an even layer.

Place the pan in the preheated 325°F oven on the middle rack. Bake for 45–55 minutes. At 45 minutes, insert a wooden toothpick into the center of the cake. If it comes out with only a few moist crumbs (no wet batter), the cake is done. If it comes out wet, bake for another 3–5 minutes and check again. The top should be deep golden brown, and the cake should smell strongly of lemon.

Remove from the oven and place on a heat-safe surface. Let the cake cool in the pan for exactly 15 minutes. This allows it to set slightly without cooling completely.

Turn the pan upside down onto a wire cooling rack. Gently tap the bottom of the pan and lift away. If it doesn't release, run a thin butter knife around the inside edge and try again. The cake should slide out smoothly. Let cool completely, about 1 hour, on the wire rack. The bottom should no longer feel warm to the touch.

Once completely cool, make the glaze: In a small bowl, whisk together 1/2 cup powdered sugar, 2 tablespoons fresh lemon juice, and 1 tablespoon milk for 20 seconds until smooth and pourable (like thin pancake batter). If too thick, add 1/2 teaspoon milk at a time. If too thin, add 1/2 teaspoon powdered sugar.

Place the cooled cake on a serving plate. Drizzle the glaze evenly over the top using a fork or whisk, allowing it to drip down the sides. Let the glaze set for 10 minutes at room temperature before slicing.

To slice, use a long serrated bread knife. Dip the knife in hot water and wipe dry between each cut for clean slices.